A Simple Bio-Instrumentation Platform for Vital-Sign Estimation Using MagnetoPleythsmography

This paper presents a simple magnetics-based instrumentation system for the estimation of two vital parameters, namely Heart Rate and Respiration Rate. A sensor-head realising the concept of magnetic plethysmography has been designed to acquire the biosignal from the human arm (i.e. radial artery). Further, an efficient electronic system and signal processor stage is designed for accurate estimation of heart rate and breathing rate. The proposed electronics include novel stages, such as (1) an improved instrumentation amplifier (for reducing artefacts and bias effects) and (2) a precision envelope estimator (for respiratory rate estimation). The design methodology of the system has been explained in the paper. Hardware prototypes of the sensor-head using a giant magnetoresistance sensor, as well as the processing electronics, have been built and tested. Studies show that the system can estimate HR with an error of less than 2 beats per minute. The non-contact working of the developed sensor-head is also proved in experimentation. Basic feasibility study on RR estimation has also been carried out. The proposed sensor system can be suitably packaged into compact modules and used in portable health monitors, ambulatory services, etc.